A borated-water core

PHYSICS · Subjective · Fermi University Physics · Nuclear Physics · Fission, fusion and nuclear energy · Fission, fusion and nuclear energy

Energy from Physics, Ch The critical reactor: neutron diffusion, buckling and the size of a core

Problem

A borated-water core, with one-group diffusion coefficient

D_c = 0.18\,\mathrm{cm}

, is surrounded by a thick reflector of ordinary water, with diffusion coefficient

D_r = 0.16\,\mathrm{cm}

and migration length

M_r = 5.9\,\mathrm{cm}

. Using the thick-reflector estimate

\delta \approx (D_c/D_r)\,M_r

, compute the reflector saving

\delta